The Advanced Art of Stop-Motion Animation: Visual Effects - Part 1
In other situations, a traveling matte can be created. This technique requires more steps and passes of the film through the camera, often done through bi-packing two strips of film together to create the various composites. One of these methods, the Williams process (named after its inventor, Frank Williams), was used for some shots on King Kong and other films. To illustrate this process for black-and-white film, I put together a digital re-creation of a film matte using a miniature dinosaur and a photo of Vancouver. First, the stop-motion puppet could be shot against a neutral or black background (Figure 9.7). The actual film in the camera, however, would capture a negative image of what was on set, creating a negative puppet against a white background (Figure 9.8). This strip of negative film was printed against another strip of high-contrast film stock, which created a silhouette of the puppet and left the background transparent (Figure 9.9). A live-action background would be shot separately and developed into a positive print. This positive print was re-printed behind the high-contrast silhouetted image of the puppet (Figure 9.10) and showing through the transparent negative space around it. The result was a new negative of the live-action background with a transparent shape of the puppet cut out of it (Figure 9.11). This negative was then combined with the original negative of the puppet, which would fit exactly into the transparent shape (Figure 9.12) and then be developed into a new positive image of both elements (Figure 9.13).
With color film, this process gets much more complicated because it essentially deals with using a blue screen as the neutral background, filtering the lens with the same color blue, and running more strips of film with alternating negative and positive images repeatedly through an optical printer. An optical printer is a combined movie projector and camera that can create composites in a similar manner to the in-camera processes, which is how special effects were done up to the digital revolution of the past 15 to 20 years. The tricky thing about these methods, other than having to think about alternating positive and negative images that are backwards, is the reliance on exact alignment of every element. If one thing goes wrong, an entire composite needs to be scrapped and repeated. Although these exact methods mostly have been phased out in today’s digital filmmaking era, it is fascinating to look back at how these cinema wizards brought classic images to the screen with what they had. These guys were true technical magicians, and their innovations can help us better understand and appreciate the tools available to us now. Everything we can do now comes from the logic behind these techniques.
Today, we have a lot more freedom allotted by digital tools that can create seamless composites and work around many of the errors and setbacks that would occur from using film. They are essentially a combination of the foundations laid by the old-school film techniques and other developments in video technology that bridged the gap to computers. One common tool used in digital imaging today is the alpha channel, which essentially makes any part of an image transparent and allows another image layered behind it to show through. This is very much a digital extension of the transparent negative image from a strip of film, and it can be created for the entire background around a subject or as any shape within an image where a transparent area is wanted. Many compositing software programs used today also have the capability of creating masks that will cut or matte out any part of an image to combine it with another. Also popular is the option of chroma keying out a blue- or green-screen background and replacing it with a live-action or digital background. This has been used for matte work on films and is also used in video production for weather reports, talk shows, and special effects.
Split-Screen and Masks
The split-screen and traveling matte processes have transitioned into the digital era using the same principles from film, but obviously with more flexibility and creative options for the filmmaker. To demonstrate some very simple techniques that can be done for compositing stop-motion with live action, I’m glad to present some contributions by Vancouver-based independent filmmaker Rich Johnson. I discovered Rich’s films online and became a big fan of his hilarious web series My Friend Barry (http://www.myfriendbarry.com), which is about a character named Frank (played by Rich) and his little blue stop-motion friend Barry. Part of the charm of the series is its simplicity, including the subtle compositing effects that bring Barry into the live-action world. Frank’s dialogue is scripted but sometimes improvised, which allows for many possibilities for having the silent animated character Barry react to the action.